1. Field of the Invention
The present invention relates to a method for achieving initial sealing between a mandrel and a billet in hydrostatic extrusion of tubes. The extrusion is carried out in a press with a high pressure chamber comprising a high pressure cylinder, a pressure generating punch insertable into the cylinder, a die arranged in the cylinder and a mandrel axially fixed in relation to the die during the extrusion and composed of a carrier and a tip attached to said carrier. Together with the opening in the die, the mandrel tip forms a gap in which a tube billet is shaped into a tube when the billet, by inserting the pressure generating punch into the cylinder, is subjected to a high, all-sided hydrostatic pressure in a pressure medium surrounding the billet.